Marco Rubio thrashed Donald Trump on the debate stage Thursday, hurling his harshest attacks of the campaign at the mogul just five days before the most crucial votes are cast in the Republican presidential primary.

The Florida senator was quick on his feet, a dramatic reversal from his wooden debate debacle earlier this month, as he tried to convince voters that the GOP frontrunner can’t be trusted to pursue conservative policies — not on Israel, not on judges, not on religious liberty, not on health care, and not even on his signature issue, immigration.

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Rubio skewered Trump for starting a “fake university” he said duped people into borrowing tens of thousands of dollars. He knocked him for manufacturing his clothing line overseas. He belittled his entrepreneurial skills, bringing up the inheritance he received from his father. And he accused Trump of a long history of hiring undocumented immigrants.

In one exchange, Rubio claimed that Trump outright lied about hiring undocumented Polish workers in the early 1980s.

Rubio even managed to turn his disastrous debate performance earlier this month into an asset. After being previously mocked for mechanically repeating a slam on Obama, Rubio turned the tables on Trump.

As he laid into Trump for a flimsy plan to replace Obamacare, Rubio accused Trump of repeating a flawed defense.

“Talking about repeating. I watched him repeat himself five times four weeks ago,” Trump said, referencing Rubio’s debate stumble.

“I saw you repeat yourself five times five seconds ago,” Rubio shot back.

One of the fiercest exchanges came over Israel. Trump insisted that though he’s pro-Israel, he would remain a neutral arbiter in negotiations for peace with Palestinians.

“The Palestinians are not a real-estate deal,” Rubio said.

“A deal is a deal,” Trump replied.

“A deal is not a deal when you’re dealing with terrorists,” Rubio countered.

Rubio is crossing his fingers that his barbs don’t come too late – that Trump’s strong trajectory heading into Super Tuesday, when a dozen states go to the polls, can be disrupted in time to prevent him from building an insurmountable delegate lead.

Even Glenn Beck, who endorsed Ted Cruz last month, had some high praise for Rubio. “Rubio is killing it,” the conservative talk show host tweeted. Rick Perry, another Cruz supporter, also gave Rubio credit. "They both did a very good job of tagging Donald of being outside the mainstream of the Republican Party," the former Texas governor and presidential candidate told reporters.

Cruz, who is locked in a fierce battle with Rubio for second place, often faded on the debate stage, but also tried to throw some bombs Trump’s way.

“This is a man for 40 years has given money to Jimmy Carter, to Joe Biden, to Hillary Clinton, to Chuck Schumer, to Harry Reid,” Cruz charged. “Nobody who supports far-left liberal Democrats who are fighting for judicial activists can possibly care about having principled constitutionalists on the court.”

Cruz often aided Rubio’s attack on Trump. Cruz specifically attacked him for “funding” the Gang of Eight politicians who spearheaded a comprehensive immigration reform effort in 2013.

Trump, again, had a sharp retort. “This is Robin Hood over here,” he responded, calling Cruz out for taking loans from financial services giants that he didn’t fully disclose on his candidacy disclosure forms.

But Trump came under fire himself for his refusal to disclose his tax returns. The mogul claimed that the documents wouldn’t be that revealing and that he can’t release them, anyhow, because he’s being audited.

"As far as my return, I want to file it except for many years, I've been audited every year. Twelve years or something like that. Every year they audit me, audit me, audit me. I have friends that are very wealthy people" who never get audited, he said.

"I will absolutely give my return but I'm being audited now for two or three [years' worth] now so I can't," he continued.

Cruz and Rubio, meanwhile, said they would release their returns over the next couple days.

The two senators didn’t spare each other in the crossfire. They bickered over who would most rapidly scrap President Barack Obama’s executive order allowing some undocumented immigrants, brought to the country as children, to remain in the country.

“I think we need a president who knows what he believes and is willing to say it on day one, not at the end of his term when it's somebody else's problem,” Cruz said.

Trump didn’t sit back and take the assault quietly. He dodged and parried with characteristic aggressiveness and lobbed attacks of his own.

“This guy’s a choke artist and this guy’s a liar,” he said, gesturing toward Rubio and Cruz, respectively. He called Cruz a “basket case” and urged him not to “get nervous.”

“You don't have one Republican senator backing you, not one,” he railed angrily at Cruz. “You don't have the endorsement of one Republican senator and you work with these people. You should be ashamed of yourself.”

And he slammed Rubio for attacking his business record.

“I’m the only one on this stage that’s hired people,” he said to Rubio. “I’ve hired tens of thousands of people. You haven’t hired one person in your life.”

Thursday’s debate came as Trump was riding a wave of momentum, coming off three successive and decisive wins, and as his rivals face a make-or-break moment before Super Tuesday.

Rubio and Cruz are both badly in need of a surge that can put them within striking distance of the real estate mogul instead of just duking it out with each other for second place. Rubio’s feistiness in particular seemed to be a strong rebuttal to his performance a few weeks earlier in New Hampshire, when his robotic debate performance – and mockery by Gov. Chris Christie – saw him tumble briefly out of the top tier. When he finished fifth in New Hampshire, he promised supporters he would never let another miserable performance happen again.

On Thursday, he was nimble and quick to rebut Trump, launching off-the-cuff counterpunches and often speaking over his rivals.

The debate underscored the emerging three-man race, with John Kasich and Ben Carson barely getting a word in.

“I don't get to talk that much,” Carson lamented, when he sought more time to answer a question on health care. Later, after another fierce exchange by the leading candidates, Carson joked, “Can somebody attack me please?”

While Rubio commanded the stage on Thursday night, it’s not clear he’ll be able to translate the success into wins on Super Tuesday.

More than 600 delegates of the 1,237 needed to clinch the GOP nomination are at stake that day, the largest single-day pot of delegates on the calendar. They’re also heavily tilted toward the South, where a band of conservative states coordinated their primaries to nudge the presidential campaign to the right.

Cruz had the most at stake entering the night. His home state is on the ballot – and his surrogates have predicted a dominant showing there, beating back suggestions that he could lose on his home court. A Monmouth poll out Thursday showed Cruz may make good on that forecast, giving him a 14-point edge over Trump.

Cruz has also bet his campaign on a banner performance across the South. His allies have spent months touting his ahead-of-the-curve organization in these states, characterizing them as a bulwark against Trump’s momentum. But Cruz’s third-place finish behind Trump and Rubio in South Carolina raised doubts about his strength in these states, and the debate will be one last chance for him to shore up support among the conservatives and evangelical voters he wants to unite behind him.

Kasich, whose campaign has been gasping for oxygen since his fifth-place showing in South Carolina and dead-last finish in Nevada, may have found some in a new Quinnipiac poll that shows Rubio trailing Trump badly in his home state of Florida. Kasich’s team leapt at the news, calling on Rubio to drop out of the contest and support a candidate more likely to win his home state. Kasich’s super PAC, New Day for America, is also airing an ad in Vermont, Massachusetts and Michigan that describes Rubio as unready to lead.

The Ohio governor, who has little infrastructure and support in the South, is banking on strong showings in Vermont and Massachusetts to keep him afloat through Super Tuesday and on track for a strong performance in Michigan, which votes on March 8, and Ohio. He’s been facing establishment and donor calls to leave the race to help the party coalesce behind Rubio as Trump’s primary alternative.

Carson, the fifth candidate on the stage has, in recent weeks, tried to capitalize on the intensifying brawling to cast himself as a calmer, more level-headed candidate, but the retired neurosurgeon has generally been a nonentity during these events, and polls show him facing an all-but-impossible chance of charting a successful path for the GOP nomination. Advisers see Super Tuesday as the end of the road for him, unless he pulls off a surprise comeback that none of the polls have seen coming.